The present invention relates to a device for recycling exhaust gas from an internal combustion engine.
A device of the type mentioned above is described in EP 0 887 340 A2. In this design, a cooling channel for cooling the system is provided within the valve chamber, which encircles the valve guide like a ring and is connected to the cooling system of the internal combustion engine.
To prevent a valve stem or valve spindle and the a valve stem guide from becoming fouled, a bushing arrangement is known from German publication DE 196 37 078 A1, in which a bushing is provided around the valve stem. This bushing serves to protect the valve stem guide against thermal radiation and contamination. The effectiveness of this bushing arrangement, however, is limited.
In German publication DE 44 24 644 C1, an exhaust gas recycling valve comprising a valve socket that is positioned within an intake channel and serves to carry the exhaust gas is described. The valve socket is enclosed by a highly thermally conductive flange, which serves to abstract high levels of heat from the hot exhaust gas, thereby allowing more cost-effective injection-molded plastic components to be used in the exhaust gas recycling system.
As is apparent from the current state of the art, devices of the type mentioned above present problems in terms of temperature. On one hand, the exhaust gas valve should be positioned as close as possible to the point at which exhaust gas exits the internal combustion engine, in order to prevent cooled exhaust gases from accumulating as a result of carbonization of the exhaust gas particles, a condition that would interfere with the functioning of the valve. On the other hand, the high exhaust gas temperatures that are required to prevent carbonization require components that are sufficiently heat-resistant, and hence cost-intensive. Furthermore, actuating the exhaust gas valve via an electromagnetic actuating mechanism, which is positioned within the valve chamber, presents a temperature problem for certain components. Due to the danger of carbonization, greater actuating forces must be used, which then require more costly components.
It is thus one object of the present invention to provide a device of the type mentioned above, with which higher exhaust gas temperatures and an effective outflow of exhaust gases can be achieved.
With an exhaust gas collection chamber according to the invention, from which the exhaust gas return line branches, an effective, low-friction outflow of exhaust causes can be attained.
This and other things are achieved via a spherical shape, which results in lower flow losses, and thus low friction losses.
Another possibility for generating low flow losses is to connect the funnel-shaped exhaust gas return line to the spherical exhaust gas collection chamber. In this manner, an angle-free, and thus low-friction, flow can be achieved.
In accordance with the invention, the valve seat of the exhaust gas valve can have a stepped contour, such that when the valve is opened, at least two different angles of aperture are created, with a smaller angle being produced when the valve is first opened.
Because the valve seat for the exhaust gas valve has a stepped contour in accordance with the invention, when the valve is opened, the smaller angle of aperture at the start of exhaust gas recycling permits significantly improved control, and thus a metered recycling of exhaust gases, with a corresponding degree of sensitivity.
Additional advantageous embodiments and further developments are specified in the claims, relating to the exemplary embodiment described in principle below, with reference to the drawings.
FIG. 1 is a longitudinal section, along the line Ixe2x80x94I in FIG. 2, of a valve chamber in an exhaust gas recycling valve,
FIG. 2 is a longitudinal section, along the line IIxe2x80x94II in FIG. 1, of a valve chamber in an exhaust gas recycling valve,
FIG. 3 is a cross-section, along the line IIIxe2x80x94III in FIG. 2, of a valve chamber in an exhaust gas recycling valve,
FIG. 4 is a perspective view of the valve chamber, and
FIG. 5 is an enlarged representation of the valve seat and the lower section of the valve.